Reapply "[fuchsia] Prepare for setting the Dart target architecture appropriately in the host binar…

runtime/bin/vmservice/loader.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of vmservice_io;
 
 _sanitizeWindowsPath(path) {
   // For Windows we need to massage the paths a bit according to
   // http://blogs.msdn.com/b/ie/archive/2006/12/06/file-uris-in-windows.aspx
   //
@@ skipping 248 matching lines @@
     }
     if (_traceLoading) {
       _log("Resolved '$uri' to '$resolvedUri'.");
     }
     return resolvedUri;
   }
 
   RawReceivePort _packagesPort;
 
   void _requestPackagesMap([Uri packageConfig]) {
-    assert(_rootScript != null);
     if (_packagesPort != null) {
       // Already scheduled.
       return;
     }
     // Create a port to receive the packages map on.
     _packagesPort = new RawReceivePort(_handlePackagesReply);
     var sp = _packagesPort.sendPort;
 
     if (packageConfig != null) {
       // Explicitly specified .packages path.
@@ skipping 880 matching lines @@
           msg[3] = null;
           msg[4] = e.toString();
           sp.send(msg);
         }
       });
       break;
     default:
       _log('Unknown loader request tag=$tag from $isolateId');
   }
 }